Enhanced Open‐Circuit Voltage in Colloidal Quantum Dot Photovoltaics via Reactivity‐Controlled Solution‐Phase Ligand Exchange

Abstract

The energy disorder that arises from colloidal quantum dot (CQD) polydispersity limits the open-circuit voltage (V ) and efficiency of CQD photovoltaics. This energy broadening is significantly deteriorated today during CQD ligand exchange and film assembly. Here, a new solution-phase ligand exchange that, via judicious incorporation of reactivity-engineered additives, provides improved monodispersity in final CQD films is reported. It has been found that increasing the concentration of the less reactive species prevents CQD fusion and etching. As a result, CQD solar cells with a V of 0.7 V (vs 0.61 V for the control) for CQD films with exciton peak at 1.28 eV and a power conversion efficiency of 10.9% (vs 10.1% for the control) is achieved.

Improved size distribution of AgBiS 2 colloidal nanocrystals by optimized synthetic route enhances photovoltaic performance

“…Monodisperse colloidal NCs as a light-absorbing layer provide reduced energetic disorder and band tail broadening, both of which are urgently required to improve solar cell performance. [24][25][26][27][28] The use of oleylamine in previous oleate-based synthetic routes enables improved monodispersity of AgBiS 2 NCs because the oleylamine not only helps the Ag precursor to completely dissolve, but also provides an efficient surface passivation of the AgBiS 2 NCs with oleic acid. 28 Surface ligands with various functional groups such as thiol, amine, and carboxylate greatly affect the chemical and physical properties of the resultant semiconducting colloidal NCs.…”

Recent Research Progress in Surface Ligand Exchange of PbS Quantum Dots for Solar Cell Application

“…The replacement of the long-chain ligands by the short-chain conductive ligands can lead to a stripped CQD surface, resulting in CQD fusion [29,49]. The polydispersity of PbS CQDs can be reduced by controlling the reactivity of ligands during the ligand exchange process [50]. For this purpose, ammonium acetate (AA, reactive species) and tetrabutylammonium acetate (TBAA, less reactive species) mixtures were employed for the solution-phase ligand exchange, and these simultaneously provided improved surface passivation and charge transport with preserved the homogeneity of the PbS CQDs.…”

Nahinfrarotaktive Bleichalkogenid‐Quantenpunkte: Herstellung, postsynthetischer Ligandenaustausch und Anwendungen in Solarzellen

“…Ein derartiger Ligandenaustausch ergab eine bessere Passivierung mit höherem Halogenidgehalt und ermöglichte die Herstellung von Bauelementen mit dickerer aktiver Schicht, die einen größeren Anteil des einfallenden Sonnenlichts absorbieren kann. Außerdem gab es verschiedene Versuche, die Grenzfläche zwischen dem halbleitenden Elektronentransportmaterial (d. h. ZnO und TiO 2 ) und kolloidalen QD‐Tinten unter Verwendung selbstorganisierender Monolagen von organischen Molekülen zu verbessern, 1) um eine bessere Bandanpassung unter Verwendung gemischter QD‐Tinten über kolloidalen Ligandenaustausch zu ermöglichen; 2) um die Leerlaufspannung zu erhöhen, indem die aus der Polydispersität der kolloidalen QDs resultierende Energiestörung über lösungsbasierten Ligandenaustausch durch Einbau von Additiven mit manipulierter Reaktivität verringert wird; und 3) um ZnO‐Elektroden für eine bessere Ladungsinjektion unter Verwendung von Halogeniden zu passivieren . In der Folge haben PV‐Bauelemente mit verarmtem Heteroübergang auf Bleichalkogenidbasis dauerhaft einen Wirkungsgrad von über 10 % gezeigt.…”